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Food Chains & Food Webs. Food Chain vs. Food Web- What’s the difference?. A food chain is a diagram that shows a step-by-step sequence of who eats whom in an ecosystem.

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Food chain vs food web what s the difference
Food Chain vs. Food Web- What’s the difference?

  • A food chain is a diagram that shows a step-by-step sequence of who eats whom in an ecosystem.

  • A food web is a diagram that shows many possible food chains or feeding relationships that can involve any combination of the individuals in an ecosystem.

  • The arrows in chains and webs always point to the organism doing the eating (Follow the Energy)


Which are the herbivores? Carnivores?

What is the significance of the arrows?

Why are decomposers important in a food chain?


Trophic levels
Trophic Levels

  • Each member of the food chain occupies a specific trophic level and describes how an organism obtains its energy.

  • The first trophic level is the producer

    • (e.g. plants) – converts energy from the sun

  • The second trophic level is the primaryconsumer

    • (e.g. herbivores)

  • The third trophic level is the secondary consumer

    • (e.g. omnivores or carnivores)



How do trophic levels differ
How do trophic levels differ?

  • The first trophic level houses the largest amount of energy.

  • Each subsequent trophic level only houses 10 percent of the energy from the previous level

    • (i.e. 90% is lost)

  • Why is energy lost at each level?

    • Not all of the organism is consumed.

    • Not everything that is eaten is digested.

    • Energy is lost as heat from the bodies of organisms.

  • What do changes in trophic levels look like as you move up through the food chain?


  • Food pyramids
    Food Pyramids

    • Food Pyramids display the distribution of organisms in a food chain through:

      • Numbers of organisms at each trophic level.

      • Biomass (kg) of organisms at each trophic level.

      • Energy (kJ) available at each trophic level.




    Pyramid of energy
    Pyramid of Energy

    • 2nd Law of Thermodynamics:

    • In every energy transformation,

    • some energy is always lost

    • There is no 100% energy conversion



    Homework
    Homework

    • Worksheets BLMs 1-9 & 1-10

    • Read 1.2 in the textbook

      • Do pg. 27 # 4-6


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